you should contact the host to look into the SMTP server error logs to determine why the email is not being relayed to that address.
Power messenger compiles the email, and sets the recipient, then passes the email to the SMTP server.
it is the job of the SMTP server to re;lay the email to the recipient.
If the the email is not getting to the recipient, the SMTP server is not relaying the email for some reason. the SMTP server error logs should contain information on why the email is not being relayed.